Hammond 1140-LU-A 10K to 600 Ohm Tube Line Output Transformer, 4:1

The 1140-LU-A is a chassis mount line output step-down transformer from the 1140 Series, designed for high performance tube line output stages. It appears as a high impedance load to vacuum tubes, so it suits tube equipment designers who need a transformer-coupled 600 ohm line output.

The impedance ratio is 10K:600 with a rated 4:1 turns ratio. Its secondary is split, so it can operate at a 4:1 or 8:1 ratio (4.08:1 / 8.16:1 typical); the drawing lists output impedances of 150/600 Ω. The 80% Ni core delivers wide bandwidth with low distortion at levels up to +23 dBu at 20 Hz into a 600 Ω load. Rated THD at 20 Hz is 0.00%, and the frequency response is -0.06 dB at 20 Hz and +0.04 dB at 20 kHz.

Typical drawing figures include 11.5 KΩ primary input impedance and 100 Ω secondary output impedance at 1 kHz and 0 dBu, 105 dB common mode rejection at 60 Hz and 90 dB at 3 kHz, THD of 0.003% at 1 kHz and 0.001% at 20 Hz (4 dBu), 610.0 Ω primary and 45 Ω secondary DCR at 20 °C, and 500 Vrms dielectric strength. Because of the Ni core, the drive signal should have no DC component.

As a line output transformer it is open style rather than housed in a Mu Metal enclosure. Leads are colour coded, including green to red/yellow for the 600 Ω secondary. The 1140-LU-A is RoHS and REACH compliant, made in Canada, and ships at 0.2 lbs (0.09 kg).